•The temporomandibular joint (TMJ) movement during swallowing was reconstructed based on motion capture.•The biomechanical response of the TMJ during swallowing was analyzed.•The movements of TMJs ...during swallowing showed two trends, and the anterior extension trend would increase the stress on the discs.
There is a close physiological connection between swallowing and the temporomandibular joint (TMJ). However, a shortage of quantitative research on the biomechanical behavior of the TMJ during swallowing exists. The purpose of this study was to reconstruct the movement of the temporomandibular joint (TMJ) based on in vivo experiment and analyze the biomechanical responses during swallowing in healthy adults to investigate the role of the TMJ in swallowing. Motion capture of swallowing, computed tomography (CT), and magnet resonance images (MRI) were performed on six healthy subjects. The movements of the TMJ during swallowing were reconstructed from the motion capture data. The three-dimensional finite element model was constructed. The dynamic finite element analysis of the swallowing process was performed based on the motion data. The range of condylar displacement was within 1 mm in all subjects. The left and right condyle movements were asymmetrical in two-thirds of the subjects. The peak stresses of the discs were relatively low, with a maximum of 0.11 MPa. During swallowing, the condylar displacement showed two trends: slow retraction and slow extension. The tendency to extend could lead to a gradual increase in stress on the disc.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Numerical models were proposed in LS-DYNA to investigate the dynamic responses and damage mechanism of rock under blasting.•The propagation of blasting stress waves and effective stress were ...analyzed together with damage evolution surrounding borehole.•A statistical damage model for rock was proposed base on Weibull distribution and the damage model parameters were fitted by SHPB tests.
The mechanical responses and damage characteristics of fractured rock masses under dynamic loads play a significant role in ensuring the safety of blasting operations. The study employs dynamic finite element method (FEM) to simulate blasting in fractured rock masses, revealing the propagation features of blasting stress waves, the evolution of effective stress and the mechanism of damage evolution around the borehole. Based on the Weibull distribution, a rock damage model was established, which yielded the stress-strain relationship and damage equation for rocks under uniaxial impact. The parameters of the damage equation were fitted through numerical SHPB tests. The results indicate that in the direction of higher initial stress, the stress wave propagates faster, and the development of damage surfaces is more pronounced. In cylindrical charge blasting, the maximum blasting stress occurs in the middle section of the borehole, with limited influence from the charge on the bottom of the hole. Within a range of approximately 2 to 3 times the borehole diameter, the surrounding rock sustains complete damage. While within a range of about 4 to 5 times the borehole diameter, the degree of damage to the surrounding rock decreases rapidly, and beyond this range, the damage to the surrounding rock gradually diminishes.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Flange tip lift crossings are widely utilized in modern tramlines to replace traditional crossings to enhance commuters’ comfort and prevent crossing nose failures. However, due to altered contact ...conditions between wheel flanges and ramps of crossings, the use of flange tip lift crossing has led to the critical issue of ramp wear. To resolve this issue, this paper investigated the dynamic contact response of a ramp during in-service loading, as well as the resultant wear of the ramp. With a dynamic finite element model, the local contact pressure and local sliding distance were computed and subsequently applied in a local contact-based wear model to evaluate the nominal wear of the ramp. Our findings indicate that under typical in-service loading conditions, the ramp exhibited up to 120 times more wear than the rail head, owing to increased contact pressure and reduced contact area during the ramp contact. To mitigate this issue, a design change of a gentler ramp inclination from the default 1:100 ramp to a 1:150 ramp could provide approximately 10% wear reduction. In addition, increasing the flange radius by 1 mm could reduce the wear by up to 13%. Conversely, increasing the speed to 45 km/h from the recommended 15 km/h speed may cause up to 5 times more wear. Furthermore, an empty tram showed 56% less wear on the ramp when compared to the condition of the maximum allowable axle load. These results offer an insight into the detrimental wear of ramps used in flange tip lift crossings of tramlines and can assist in the development of new designs and operating guidelines to mitigate ramp wear.
•Ramp wear of a tram crossing was investigated using dynamic finite element simulation and a local contact-based wear model.•The wear of the ramp was found to be up to 120 times greater than that on the rail head of tram rails.•Gentler ramp inclination, increased flange radius, reduced vehicle speed and lower axle load can reduce the wear of the ramp.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•In the current study, behaviors of steel double-hat section components under axial quasi-static and impact loading have been studied experimentally and numerically. The test data points out to the ...consistent load-shortening behaviors of fully adhesively-bonded components with respect to conventional spot-welded hat sections as well as hybrid components with discontinuous adhesive lines supplemented with sparse spot welds.•A close scrutiny of deformed specimens, however, has revealed a disconcerting failure mode of flange separation in fully adhesively-bonded components which appears to get aggravated with higher impact velocity and consequently, impactor kinetic energy.•A robust finite element modeling methodology for predicting the behaviors of adhesively-bonded joints with steel substrates has been demonstrated. Using a cohesive zone material model in LS-DYNA with independent shear and normal fracture properties of the deployed adhesive provided as input data, its capability to predict well behaviors of both single lap shear and T-peel joints under tensile loading setups in a UTM has been shown, perhaps for the first time. Welded joints have been modeled with special spot weld elements in LS-DYNA.•The modeling procedure for joint coupons mentioned above has been extended to the study of behaviors of double-hat section components of different types i.e. spot-welded, fully adhesively-bonded and hybrid (i.e. discontinuously bonded with sparse spot-welds). The power of the current explicit finite element analysis-based approach in consistently predicting test load-displacement curves as well as relevant crash metrics such as initial peak and mean loads, and absorbed energy has been established. Finally, the current finite element modeling procedure appears to be quite effective in performing the challenging task of predicting the deformed shapes of hat section components including separation of flanges in fully adhesively-bonded components.•In summary, the reported study has provided insights into the behaviors of adhesively-bonded steel double-hat section components with respect to conventional spot-welded members under axial impact loading through tests carried out in a drop-weight setup, and detailed a comprehensive finite element modeling approach for predicting the test responses and deformed shapes of specimens.
A significant consideration in the deployment of adhesively-bonded joints in applications such as automotive body structures is their performance under impact loading. Due to the distinct behaviors of an epoxy-based structural adhesive under normal and shear loads combined with its propensity to undergo brittle fracture in cohesion and adhesion, special care needs to be taken in the constitutive modeling of such an adhesive as traditional Von Mises type yielding and elastoplastic material behavior do not seem to be applicable. In the current study, to start with, experimental load-displacement behaviors till failure of single lap shear and T-peel joints with steel substrates are predicted with the aid of a cohesive zone material model using LS-DYNA, an explicit nonlinear finite element analysis solver. With confidence established on cohesive zone modeling of the joints mentioned, the procedure is extended to robust prediction of the load-displacement responses and deformed shapes of steel double-hat section components subjected to axial impact loading. Three variants of steel hat section components have been considered from the viewpoint of joining of flanges with conventional discrete spot-welds, only continuous adhesive bonding, and a hybrid configuration with a combination of adhesive bonding and sparse spot-welds. The study reported here provides insights into mechanical behaviors of adhesively-bonded steel double-hat sections under impact loading, and demonstrates an efficient finite element modeling approach for adhesively-bonded steel hat sections using cohesive zone elements with fracture mechanics-based criteria for failure.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A meso-scale numerical model is developed to investigate the dynamic tensile behaviour of concrete in spall tests.•The dynamic fracture process of concrete is successfully captured by the proposed ...rate-dependent cohesive model.•The micro cracking process in the meso structure is explicitly represented.•The influences of fracture properties in different constituents and mesostructure are discussed.•The results show good agreement with the experimental data over a wide range of strain rates.
We present a two-dimensional meso-scale finite element model for simulating the dynamic tensile behaviour of concrete. Aggregate, mortar and interface transition zone (ITZ) are explicitly modelled at the meso-scale. Rate-dependent cohesive elements, which take into account the effects of the viscosity occurring in the fracture process, are dispersedly pre-inserted to simulate the nucleation, coalescence, and propagation of cracks. The proposed model is validated by comparing with the experimental data of spall tests. The evolution of microcracks of concrete under dynamic loading is presented. The influences of the fracture parameters and the mesostructure on the dynamic tensile strength are investigated. The results suggest that the property of ITZ plays an important role on the dynamic tensile behaviour of concrete. The tensile strength and dissipated fracture energy under dynamic loading are affected by the mesostructure of concrete as well.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In the framework of dynamic finite element methodology, this articleinvestigates the free and forced vibration behaviors of functionally graded double wishbone structural systems considering the ...deformability of links and joints. Due to the advantages of the functionally graded materials (FGMs), the double wishbone control arms are modeled as a plane functionally graded frame based on the Timoshenko beam theory (TBT). The power law is adopted to model the through-thickness material gradation. Based on the power gradation law, analytical expressions for the equivalent material stiffnesses and the equivalent inertia are derived. On the other hand, joint deformability is modeled using flexible translational and rotational springs. The dynamic equations of motion are derived based on the Hamiltonian principle. Based on the isoparametric Timoshenko plane frame element, a displacement-based dynamic finite element model is developed. The accuracy of the developed numerical procedure is verified for both free and forced vibration behaviors and good agreement is obtained. Numerical results are obtained and discussed. The results show the significant effects of the FGM distributions on the free and forced vibration behaviors. The developed procedure and the obtained results are supportive of the design and manufacturing processes of such structural systems.
Full text
Available for:
BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
The deployment of asphaltic support layers (ASLs) within railway track structures has the potential to increase track bending stiffness, assist moisture runoff and provide a platform for track ...construction. These merits have increased its usage within the rail industry, however the understanding of asphaltic track dynamics during train loading remains limited. Therefore, the primary aim of this study is the development of new knowledge into the dynamic behavior of concrete slab track systems enhanced with asphaltic underlays. To do so, a numerical simulation approach is used, comprised of two sub-models: 1) a coupled multi-body vehicle−track model, for the purpose of computing wheel/rail forces; and 2) a 3D dynamic finite element track-ground model to simulate stress wave propagation in the sub-structure. The models are validated using both analytical results and field tests, and then used to simulate slab track systems with ASL thicknesses of: 0, 0.05, 0.07, 0.10, and 0.15 m. First the dynamic response at locations both near and far from the track joints are compared to quantify the asphaltic foundation stresses, deflections, accelerations and strains. It is found that stress concentrations occur near the concrete base joints and are an important consideration for ASL design. Next, asphalt concrete durability at 400 km/h line speed is explored considering seasonal temperature variations and it is found that the expected cumulative damage meets serviceability requirements. Finally, the influence of different asphaltic layer thicknesses on reaction modulus is discussed, concluding that the optimal thickness range, considering plastic deformation and construction constraints, is between 0.07 m and 0.10 m.
•A hybrid modelling approach is proposed to assess dynamic performance of asphaltic slab tracks.•Effect of asphalt on stresses, deflections, accelerations, and strains is quantified considering slab expansion joints.•Asphalt concrete durability and its implications for asphaltic trackbed design are discussed.•An optimal thickness range for asphaltic support layers is between 0.07 m and 0.10 m
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The pre-stress of the temporomandibular joint (TMJ) at the intercuspal position (ICP) was often neglected, which would cause errors in the finite element analysis. The purpose of this study was to ...investigate the effect of pre-stress on dynamic finite element analysis of the TMJs. One healthy female adult was recruited for medical imaging and motion data acquisition of the reference position (RP) to the ICP and the clicking teeth. The three-dimensional maxillofacial model including the maxilla, mandible, articular cartilages, discs, and discal attachments was reconstructed. Motion from the RP to the ICP was simulated to obtain pre-stress at the ICP. Two groups of the clicking teeth were simulated: (1) the group without pre-stress (GWoP); (2) the group with pre-stress (GwP). Significant differences were found between the two groups at the initial moment of movement, during the open-mouth phase, and during the collision phase between the upper and lower teeth. The maximum difference in the discal contact stress between both groups was even more than double. The relaxation of the TMJ at the beginning of the mouth opening was simulated in the GwP. In addition, an increase in the TMJ stress during teeth tapping was simulated in the GwP. These were not reflected in the GWoP. If pre-stress at the ICP was not considered, part of the true results would be lost. It is necessary to consider pre-stress in the dynamic finite element analysis of the TMJ.
Full text
Available for:
BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Significance of the paper for the research community•There is a pressing need to accurately simulate the deformation, damage and failure of composites under impact conditions as composites are ...increasingly being used for automotive and aerospace applications.•This paper addresses this need by describing an integrated framework of analytical, numerical and experimental approaches that should be of interest to composite researchers.Original and new work•The orthotropic visco-elastic-visco-plastic material model for composites as discussed in the paper is new, and presents a novel way deformation, damage and failure are handled in a modular fashion.•Theoretical and implementation details of the three components are discussed in the context of modeling impact events. The constitutive model is implemented in LS-DYNA, a commercial explicit dynamics finite element program. Four high velocity impact tests are conducted to yield validation data that are then used to evaluate the developed constitutive model.•Results indicate that developed procedures and improvements provide the analyst with a reasonable and systematic approach to building predictive impact simulation models.
Researchers have met the challenge of modeling impact events involving composite targets for a variety of applications in a variety of ways. In this paper, the theory and implementation details of an orthotropic visco-elastic-visco-plastic material model with strain rate dependence are discussed. The model is driven by experimental data from quasi-static as well as high strain rate tests, and the data is used in defining the deformation, damage and failure sub-models. Validation data is generated by shooting a hollow 50 g Al-2024 projectile at different velocities against a flat panel target made of unidirectional composite material in a 16-ply (0/90/45/-45)2S layup. Explicit dynamic finite element analyses of four high speed tests involving one contained (projectile rebounded) and three uncontained (projectile penetrated) impact tests show that the developed material model and modeling techniques yield reasonable and acceptable predictions.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
PDF